Method and composition of matter for surface-treating aluminum



Patented Aug, 9, 1927.

UNITED STA TES- PATENT OFFICE.

ALAIDAR PACZ, OF EAST CLEVELAND, OHIO.

METHOD AND COMPOSITIONOF MATTER FOR SURFACErTBEATING ALUMINUM.

1T0 Drawing.

and an alkali salt. The fluo-silicate employed is preferably that of sodium which is the cheapest and most readily available, although I do not limit myself thereto, a very convenient, satisfactory and effective concentration in practical use is that wherein the bath contains 0.15% of this material, but I do not limit myself to this strength. By non-ferrous, iron-group, metal I intend to designate nickel and cobalt and any convenient salt thereof can apparently be used. I have had excellent success with the sulphate, nitrate, and chloride of these metals. A very convenient and practical concentration of the same is from 0.2% to 0.3%, although I do not limit myself thereto. By alkali salt I designate salts both of the fixed alkalies and of the volatile alkali, and the particular salt which I prefer to use is the nitrate although I have had a measurable degree of success with such other salts as the phosphate and sulphate. In using ammonium, sodium, or potassium nitrate I have found that 1% is a very satisfactory concentration although I do not limit myself thereto. It appears to be necessary that this third ingredient be preponderant.

The solution is preferably employed hot, even up to the boiling point, and the articles to be treated are immersed therein for a greater or less length of time as determined by the extent of treatment desired which can readily be judged by the eye. The effect of this treatment is to produce upon the surface a mottled, speckled, or spotted appearance, irregular portionsof varying sizes and shapesbein covered with a dense adherent,

dark, deposit intermingled with streaks and ridges of color. In general the more concentrated the solution or the higher the temperature the smaller are the s ots and the finer grained the design; an also the more rapidly the process is performed. Variations in the relative quantities of the ingredients bright and unaffected aluminum Application filed February 19, 1928. Serial No. 87,463.

also affect the size of the grain and the mann nor of the ornamentation. 1n the amount of the fiuo-silicate produces a finer grain and a decrease tends to coarsen the same. .An increase in the amount of the iron grou metal produces a much similar change 0 the graining. The effectof the alkali salt appears more especially to influence the strength or depth of the colorization which becomes faint with low con- Thus an increase centrations and darker and blacker withgreater strengths.

The resulting coating is unaffected by heat and is highly resistant to abrasion even that of a steel brush, the unmodifiedaluminum surface yielding rather than the modified 'or coated portion. By the use of proper concentrations and temperatures the surface can be very thoroughly covered with the coating described. Care however, must be observed not to permit too great proximity between metallic articles receiving simultaneous treatment. Stencils or other protective means can be employed if desired to shield any desired portion against the action of the solution. The solution can be used repeatedly although additions of the several ingredients are required from time to time. Eventually the solution becomes sufiiciently contaminated with impurities, partly dissolved from the articles and partly of accidental entrance so that it must be discarded.

The articles after receiving the treatment hereinbefore described can be subjected, if desired, to further treatments designed to color the unmodified portions, or may be' covered with paint, lacquer, etc, which adheres much more strongly thereto than to the unmodified metal. Alloys of aluminum with other metals.

such as silicon, magnesium, zinc, copper and the like are likewise'susceptible to this process, although in many cases the surface does not exhibit the striking contrast between the color of the modified and unmodified portions which is presented by pure aluminum. For example an alloy of aluminum and silicon treated in this manner exhibits areas of lead color interspersed with areas of a comparatively light grey, the whole resembling marble.

It will be understood that I, do not limit myself to the concentrations herein described nor to the particular salts above enumerated except within the limits specifically indie Within its own class and I do not limit myself except as specifically set forth in my several 7 claims.

Having thus described by invention what I claim is:

1. The process of surface treatin metallic articles consisting at least super cially of aluminum which contains the step of immersing the article in a solution containing a soluble fluo-silicate, a salt of a non-ferrous iron-group metal, and an alkali salt.

2. The process of producing an irregularly mottled aluminum surface which contains the step of subjecting a clean aluminum surface to the simultaneous action of a soluble ac flue-silicate, a salt of a non-ferrous iron group metal, and an alkali nitrate.

3. The process of providing aluminum 4. As a composition of matter, adipping solution for aluminum articles containing a soluble lino-silicate, a soluble metallic salt,

and a neutral alkali salt. 1

. second a metallic salt,and the third a neutral alkali salt.

5. As a composition of matter, a dipping I solution for aluminum articles comprising a soluble flue-silicate, a soluble salt of a nonferrous metal of the iron group, and an alkali nitrate, all dissolved in water.

i In testimony whereof I hereunto afix my signature.

ALADAR PACZ. 

